In telecommunication systems, links are established between nodes of a system for conveying information. Efficient use of these links requires enforcement of communication parameters defining when nodes at each end of a link anticipate information from the other unit. These parameters, in efficient bandwidth systems, comply with extremely tight tolerances to maximize information exchange. These parameters may include propagation delay between nodes of a network and transmit frequencies combined with any path introduced frequency error such as Doppler frequency shifts. As the communication parameters of the interfacing nodes become more predictable and precise, guardbands on communication channels such as frequency and timeslots can be reduced to accommodate exchange of additional information.
In conventional static or lightly dynamic telecommunication networks, these communication parameters may be refined upon the establishment of a communication link and relied upon throughout a communication session. However, in a dynamic communication system where these communication parameters are rapidly changing, communicating nodes such as subscriber units must continually refine and update these communication parameters in order to maintain the prescribed tolerances of the system.
Many systems evaluate each transmission employing dynamic communication parameters to determine the precision of the employed parameters. When the parameters exceed a threshold value as defined by system specifications such as channelized communication frequencies or timeslots, the receiving system informs the transmitting node of correction values necessary to bring the communication parameters into compliance with the system requirements.
This approach is suitable when established communication links are not susceptible to transient effects such as temporary outages due to obstructions or fleeting interference. However, in dynamic communication systems where communication parameters are short-lived, even brief outages of communication links cause communication parameters to become stale and ineffective when utilized following communication link outages. A node such as a subscriber unit that employs out-dated communication parameters will not be recognized by a receiving system due to the precise tolerances of channelized communication systems. When a subscriber unit is not recognized, the communication link will be terminated. Reestablishing a communication link is both inefficient and annoying for communication link users.
Furthermore, systems that attempt to predict communication parameters based on historical values, may be ineffective when a communication link is interrupted and one of the communication nodes such as a subscriber unit unpredictably alters its direction of travel causing an introduction of unanticipated Doppler frequency and timing variations. The prediction of communication parameters then becomes ineffective when the link obstruction ceases.
Accordingly, there is a significant need for a method and apparatus for predicting dynamic communication parameters continuously throughout a brief outage such that when the outage is terminated, a subscriber unit will have revised its dynamic communication parameters to comply with the current system dynamics. The subscriber unit may then immediately employ these revised dynamic communication parameters in subsequent transmissions to a receiving unit. The receiving unit will recognize and process the received communications since the revised communication parameters are in compliance with system parameters, thus foregoing the need to establish a subsequent communication link.